Operational distribution pipes contain a fluid (water, for example) whose pressure is constantly fluctuating. Some fluctuations are high in magnitude and occur over hours or days and others are lower in magnitude but happen at a much higher frequency (in the order of 1 Hz). In comparison, a transient event is a rapid, unusual, short duration deviation from normal operation (typically a few seconds) which is large in magnitude.
In water supply networks, pipe pressure must be carefully controlled in order to maintain a consistent supply to the customer, protect the network infrastructure and adhere to regulatory guidelines and laws. Unfortunately the control systems currently in place do not always maintain a constant pressure. Indeed, given the nature of the network, it is practically impossible to do so, and aspects of the control system's operation often give rise to pressure transient events.
There are many causes of pressure transient events on water pipes. For some of these events, the cause can be easily identified but for other events the cause is not clear. A non-exhaustive list of events which cause a pressure transient would include:                Fast opening/closing of a valve on a long supply line resulting in a water hammer effect.        Equipment failure (pump, PRV (pressure regulating valve)).        Water main burst.        Diurnal usage pattern.        Configuration changes (opening/closing of boundary valves).        Pumping events (filling water towers etc.).        Un-moderated industrial and commercial customers.        
Pressure transients can stir up the sediment in the pipe, causing water discolouration and brown water events. These events are monitored by the regulator in the United Kingdom and will result in low performance scores for the operating company and possible fines. Pipelines which have corroded, have failing joints or have been otherwise damaged can be caused to fail by a pressure transient. A low pressure transient (below the surrounding pressure) can cause water to be drawn into the main, via a leak for example, bringing with it potentially harmful unclean and uncontrolled water.
Trying to discriminate real transients from the background noise using rate detection and thresholding is prone to: error, missing key events, and producing false positives. Such an approach has been adopted in the past with varying degrees of success. The pressure data for such an analysis is commonly acquired by a logging device attached to the pipeline that stores all measured pressure values for a duration of, typically, several weeks. The logger is then retrieved, the data down-loaded into a computer and then analysed. The fundamental disadvantage with this approach is that the operator of the pipeline does not receive any information about a transient event until some considerable time after it has happened. The information is then so out of date that its value has diminished considerably.